The Collaborative International Dictionary of English v.0.48:

Abnormality \Ab`nor*mal"i*ty\, n.; pl. Abnormalities.
   1. The state or quality of being abnormal; variation;
      irregularity. --Darwin.
      [1913 Webster]

   2. Something abnormal.
      [1913 Webster]

WordNet (r) 3.0 (2006):

abnormality
    n 1: an abnormal physical condition resulting from defective
         genes or developmental deficiencies [syn: abnormality,
         abnormalcy] [ant: normalcy, normality]
    2: retardation sufficient to fall outside the normal range of
       intelligence [syn: abnormality, mental defectiveness]
    3: marked strangeness as a consequence of being abnormal [syn:
       abnormality, freakishness]
    4: behavior that breaches the rule or etiquette or custom or
       morality [syn: abnormality, irregularity]